Dust-tight locking mechanism



Feb. 20, 1968 'w.- H. EDWARDS DUST-LIGHT LOCKING MECHANISM Filed May 2, 1966 3 Y INVENTOR. Y rV/umn/ifarmkos mm Maw United States Patent F 3,369,653 DUST-TIGHT LOCKING MECHANISM William H. Edwards, St. Paul, Minn., assiguor to Mmnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed May 2, 1966, Ser. No. 546,718 5 Claims. (Cl. 20652) ABSTRACT OF THE DISCLOSURE Mechanism for releasably locking a cover to a base wherein an expandable elastic cup is fitted to an opening in the cover. The fully enclosed wall of the cup projects beyond the inside of the cover and may, in its normal condition, be freely inserted into a socket in the base. A plunger having a relatively large shoulder portion is moved longitudinally within the cup to force the shoulder into a constriction of the cup, thus expanding the cup to fill the-socket and lock the cover to the base.

This invention relates to a locking mechanism useful for securing dust-tight closure of tape and film reel cases and the like.

It is desirable to maintain tapes and films, e.g. computer tapes and the like, in dust-free cases or containers. Such as case comprises a base having a circular bottom wall with a peripheral upward extending rim and a cover having a circular top wall with a peripheral downward extending rim. A tape reel is contained within the rim of the base, and the rim of the cover fits around the base rim and abuts a gasket ring at the outside edge of the bottom wall to completely enclose the reel. The central opening in the hub of the reel (provided therein for mounting the reel when in use) enables an expandable elastic member extending from the cover and through the reel to interconnect with a socket in the base. This locking mechanism holds the case shut for secure, airtight closure and prevents accidental opening while the case is being handled.

The interconnection between the expandable elastic member of the cover and the socket of the base is accompished by means which laterally expands the member to frictionally grip the wall of the socket. As far as I am aware, in the cases that have been heretofore commercially available, such expansion has been provided by a rubber gasket mounted on a stud with means for compressing the gasket longitudinally, e.g. by turning a handle to squeeze the gasket between the head of the stud and the wall of the cover. For example, see US. Patent No. 3,074,546, issued to F. H. Burgess et al. I

In variance therefrom, the expandable elastic member of my locking mechanism comprises an expandable elastic cup aflixed to the cover. The inner wall of the cup is provided with a peripheral rib which defines a reduced opening or constriction within the cup. A plunger in the cup has a shoulder portion that is greater in cross section than the normal opening at said constriction. In closing the case, the cup is first positioned within the socket of the base and then the plunger is moved to force the enlarged shoulder portion into the constriction of the cup. The outside diameter of the cup, accordingly, is

caused to expand within the socket and thereby frictionally grip the socket wall.

The present invention thus involves a simple push-pull movement which easily provides sufiicient force for expanding the cup, whereas the prior devices typified by the Burgess et al. patent require a torque movement for the application of sufiicient manual force to compress a gasket. The locking mechanism of my invention like that of Burgess et al. provides a dust-tight seal but is less com- 'ice reference to the following detailed description and drawing wherein:

FIGURE 1 is a side view, shown partly in section, of a reel case incorporating a locking mechanism of my invention;

FIGURE 2 is an enlarged and partially sectional view of the plunger for the locking mechanism of the case shown in FIG. 1; and

FIGURE 3 is an enlarged partially sectional view of the expandable cup for the locking mechanism of the case shown in FIG. 1.

Referring to the drawings, a reel case has a base 12 and a cover 14. The base has a circular bottom wall 16 with an upwardly extending peripheral rim 18 for containing a film reel. The cover has a circular top wall 20 with a downwardly extending peripheral rim 22 which fits outside the rim 18 of the base and abuts a sealing gasket ring 24 on the edge of the bottom wall 16 to effectively enclose the interior of the case.

The rim of the base has four cut-out portion 54, posi tioned at intervals. These cutouts provide a means for manually gripping a reel contained in the base at opposite points on the edge of the reel flange for removing the reel from the case. A circular ridge 56 on the bottom of the base fits inside a circular ridge 58 in the cover when a plurality of the cases are stacked one on top of the other. Slots or openings 60 in the ridge 56 provide venting to the space within the flange when the case is placed on a flat surface. Without the venting, an objectionable suction gripping of the case to the flat surface can result.

The base has a central inset 26 having a socket 28. The cover also has a central inset 30 corresponding to the inset 26 of the base. Said inset portions are partially inserted into each side of the hub opening of a film reel when a reel is contained within the case. Said inset portions are thus in close adjacency as illustrated while the case is closed.

A cushion ring 62 around each of the inset portions provides a cushion seating for the film reel. The resilient flange 64 of the cushion ring 62 is biased inward of the case walls and further supports the reel to avoid lateral play or movement.

An expandable locking member comprising a tapered elastic cup 32 is fitted to an opening in the inset 30 of the cover and extends into the socket 28 0f the base when the case is closed. The inset of the cover is further provided with a shield member 34 to cover the exposed sharp edges of the inset, to help seal around the expandable cup and prevent leakage into the enclosure through the said cover opening, and to enhance the appearance of the case. A plunger 36 within the cup 32 is designed for longitudinal push-pull movement therewithin. A handle 38 of the plunger 36 is provided on the outer end of the plunger 36 and is available for manual longitudinal movement from outside the container. The cup is completely enclosed except for a mouth 33 provided for the longitudinal movement of the plunger and therefore does not breach the air-tight dust-pr00f closure of the case.

An annular rib 40 on the inner wall of the expandable cup defines a reduced opening or inner constriction. The plunger 36 has a retaining flange 42 at the inserted end thereof, a recessed portion 44 adjacent to the flange, and a shoulder portion 46 .adjacent to the recessed portion. The cross section of the plunger at its flange 42 and shoulder portion 46 is greater than the opening defined by the rib 40 of the cup, whereas the cross section at the recessed portion 44 of the plunger is equal to said opening defined by the rib 40.

The plunger has a central chamber 48 that is open at the inserted end thereof to the bottom of the cup. Said chamber extends through the length of the plunger and into the handle 38, and a passage 50 provides an air vent from outside the case into the chamber 48.

In operation, to position the locking mechanism in its release or unlocked position, the plunger is withdrawn from the cup to the extent permitted by the retaining flange 42. The recessed portion 44 of the plunger is thus in the rib opening and the cup is in its non-expanded condition. In this unlocking position of the plunger, the cover can be placed on or removed from the base.

To close and lock the case, the cover is positioned over the base so that its rim 22 is sealed against the peripheral gasket 24. In such position the expandable cup 32 is seated within the socket 28 of the base. With the Plunger 36 in the unlocking position, the mating edges 52 of the rib 40 and shoulder 46 are tapered and enable the plunger to be easily pushed to force the shoulder portion 46 into the restricted opening of the rib 40. To accommodate the larger shoulder portion, the rib opening is caused to become enlarged and accordingly, the outer dimension or circumference of the cup is expanded to fill the opening of the socket and frictionally grip the wall thereof. This locking position of the plunger is illustrated in FIG. 1. The cover is thus held fast to the base until the plunger is pulled back to the unlocking position at which the recessed portion is again positioned within the rib opening to allow the cup to return to its normal circumference and thereby release the frictional grip on the socket wall.

As the plunger is pushed and pulled longitudinally Within the cup, the void volume in the enclosed bottom portion of the cup is varied in accordance with the space that is alternately occupied and then vacated by the plunger. Such movement would induce a change in pressure within the said bottom portion of the cup which would tend to resist the position changes of the plunger. Such pressure changes are, however, obviated in my locking mechanism by the chamber 48 and vent passage 50 which communicate the said bottom portion of the cup to the outside. Lateral vent openings are preferred to an extension of :the chamber upwardly through the top of the handle :to enable trademark labels or the like to be applied to the top of the handle, e.g. in the form of .an indicia hearing replaceable disc insert 53. Obscure lateral vent passages below the handle are also believed less likely to become plugged with foreign matter or inadvertently covered by the operator when he grips the handle.

The locking mechanism above described is subject to :numerous variations without departing from the scope of :my invention. Thus, for example, the shoulder of the plunger can be provided with a ridge or ridges that grip the rib of the cup to hold the plunger in a locked position. A positive withdrawal of the plunger is thus required and the lock will not likely be accidentally released.

My invention is thus not limited to the device as distclosed herein but by the following claims.

I claim:

1. A dust-tight mechanism for releasably locking a (cover to a base, said mechanism comprising (1) an expandable elastic cup fitted to an opening in said cover, which cup has (a) a mouth opening to the outside of the cover and (b) a fully enclosed wall projecting beyond the inside of the cover and having an inner constriction,

(2) a plunger extending through the mouth into the cup, which plunger has (a) a portion of greater cross section than the normal opening at said inner constriction and ,(b) a handle available at the outside of the cover for moving the plunger longitudinally between a locking position at which its portion of greater cross section coincides with said constriction to expand the cup and an unlocking position at which it does not expand the cup,

(c) vent passage means for venting the interior of the cup to the outside of the cover, and

(3) a socket in the base into which the projecting wall of the cup may be freely insertedwhen the plunger is in the unlocking position, and which the cup fills to frictionally lock the cover to the base when the plunger is moved to the locking position.

2. A dust-proof reel case comprising a base and a cover each having a central inset portion and a dust-tight mechanism mounted at the central inset of the cover for releasably locking the cover to the base, said mechanism comprising (1) an expandable elastic cup fitted to an opening in said cover, which cup has (a) a mouth opening to the outside of the cover and (b) fully enclosed wall projecting beyond the inside of the cover and having an annular rib on the inner wall affording an inner constriction, (2) a plunger extending through the mouth into the cup, which plunger has (a) a shoulder portion of greater cross section than the normal opening at said inner constriction,

(b) a recessed portion having a cross section no greater than said normal opening,

(0) a handle available at the outside of the cover for moving the plunger longitudinally between a locking position at which its shoulder portion coincides with said constriction to expand the cup and an unlocking position at which its recessed portion coincides with the constriction,

(d) a central chamber that opens into the bottom of the cup and a vent passage communicating the chamber with the outside of the cover for relieving air pressure changes within the cup as the plunger is moved between its inner and outer positions, and

(3) a socket in the central inset of the base into which the projecting wall of the cup may be freely inserted when the plunger is in the unlocking position, and which the cup fills to frictionally lock the cover to the base when the plunger is moved to the locking position.

3. A reel case as defined in claim 2 wherein each of the exterior of the plunger and the interior of the cup and the socket is circular in cross section, and the plunger between its shoulder and recessed portions and the rib of the cup have tapered surfaces which mate when the plunger is in the unlocking position, which taper facilitates movement of the shoulder portion of the plunger into the area of the rib.

4. A dust-proof reel case comprising a base and a cover, said base having a generally flat circular bottom wall with a central inset, an upwardly extending rim, and a sealing gasket ring at the edge of the bottom wall, and said cover having a generally flat circular top wall with a central inset and a downwardly extending peripheral rim which, when the case is closed, overlaps the rim of the base and abuts said gasket ring to afford a seal at the edge of the case, and a dust-tight mechanism mounted at the central inset of the cover for releasably locking the cover to the base, said mechanism comprising 1) an expandable elastic cup of circular cross section fitted to an opening in said cover, which cup has (a) a mouth opening to the outside of the cover,

and

(b) fully enclosed wall projecting beyond the inside of the cover and having a uniform annular rib on the inner wall aifording an inner constriction, (2) a plunger of circular cross section extending through the mouth into the cup, which plunger has (a) a shoulder portion of greater cross section than the normal opening at said peripheral rib,

(b) a recessed portion having a cross section approximately equal to said normal opening at the peripheral rib,

(c) a handle adjacent said shoulder portion and available at the outside of the cover for pushing the plunger to a locking position at which its shoulder portion coincides with said rib to expand the cup and for pulling the plunger to an unlocking position at which its recessed portion coincides with the rib, and

(d) a vent between the interior of the cup and the outside of the cover, and

(3) a circular socket in the central inset of the base into which the projecting wall of the cup may be freely inserted when the plunger is in the unlocking position, and which the cup fills to frictionally lock the cover to the base when the plunger is moved to the locking position.

5. A dust-tight mechanism for releasably locking a cover to a base including an elastic member mounted on the cover which may be freely inserted into a socket in the base and expanded to fill the socket and thus frictionally lock the cover to the base, wherein the improvement comprises:

(1) the expandable elastic member is a cup which has a mouth opening to the outside of the cover and a fully enclosed wall having an inner constriction and (2) a plunger in the cup has a portion of greater cross section than the normal opening at said constriction and has a handle for longitudinal push-pull movement between a locking position at which its portion of greater cross section coincides with said constriction to expand the cup and an unlocking position at which it does not expand the cup, said plunger including vent passage means for venting the interior of the cup to the outside of the cover.

References Cited UNITED STATES PATENTS 2,956,468 10/ 1960 Macy -72 3,13 8,250 6/ 1964 Burgess et al. 206-52 FOREIGN PATENTS 1,229,823 3/1960 France.

1,306,092 9/ 1962 France.

WILLIAM T. DIXSON, JR., Primary Examiner. 

